1. Field Of The Invention
This invention relates to plastic netting, and more particularly to an extruded bicomponent elastomeric netting having bidirectional elasticity, that is elasticity in both the machine direction and the transverse direction. Such netting is sometimes referred to as fiber formed netting because the strands making up the netting are individually extruded from a die.
2. Description Of The Related Art
For purposes of the present invention, the terms "cross machine direction" and "transverse direction" are synonymous and referred to as "TD", as are the terms "longitudinal direction" and "machine direction", referred to as "MD". Current production of elastomeric roll goods, such as scrims, sheets, films, foams, nettings, nonwovens, fibers, threads and the like are basically isotropic, exhibiting essentially the same properties in all directions of their two dimensional plane. However, in many applications, different elastomeric properties are desired in different directions, i.e., in the MD and TD. Although numerous patents exist describing netting, woven and non-woven fabrics, meshes and chain nets with bicomponent materials, they do not provide any suggestion to modify the prior art such as is done in the present invention with respect to extruded plastic net. Existing technology does not include an extruded bicomponent elastomeric netting with bidirectional elasticity. A bicomponent netting is a netting in which the two sets of strands (MD and TD strands) are made up and fed by two separate (and possibly different) polymer melt streams.
Nets, wovens and nonwoven reinforcements made of more than one material are disclosed in U.S. Pat. No. 4,636,419 to Madsen, U.S. Pat. No. 4,241,123 to Shih, and U.S. Pat. No. 4,460,633 to Kobayashi et al. In addition, a netting die fed by two separate polymer streams is disclosed in U.S. Pat. No. 3,791,784 to Arechavaleta.
U.S. Pat. No. 4,636,419 issued to Madsen et al. on Jan. 13, 1987 discloses a "Net and Method of Producing Same" which employs a combination of side by side extrusion streams, transversal embossment, and splitting to produce netting composed of a regular array of longitudinal ribbon-formed continuous polymer filaments and a regular array of transverse stems or strands of a different polymer matter. It is disclosed that the use of two different polymer substances in two directions affords netting of interesting and unusual properties (col. 2, lines 12-25 and 30-31). In Example 1, the cross machine component comprises Nylon 6 and the machine direction component comprises polypropylene (col. 11, lines 13-31). It is disclosed that elastomeric netting may be prepared by the method of this patent, and preferred materials as well as a suitable application for such netting is disclosed (col. 9, line 67 through col. 10, line 7). Bidirectional elasticity in net as-extruded is neither disclosed nor suggested.
U.S. Pat. No. 4,241,123 issued to Shih on Dec. 23, 1980 discloses non-woven netting wherein a first group of melting monofilaments are die extruded and a second group of monofilaments or a yarn is crossed, pressed, and welded to form a welded plastic netting (col. 3, lines 8-12).
U.S. Pat. No. 4,460,633 issued to Kobayashi et al. on Jul. 17, 1984 discloses a nonwoven reinforcement for resinous composites made of bundles of non-twist or soft twist yarns as warps on both sides of bundles of non-twist or soft twist yarns as wefts, warps and wefts being bonded by an adhesive agent impregnated into the wefts.
U.S. Pat. No. 4,980,227 issued to Sekiguchi et al. on Dec. 25, 1990 discloses a stiff, netlike sheet of heat bonded five layer and three layer polyolefin yarns which exhibits retention of its sheet-like shape due to its stiffness. Although heat bonding of polyolefin materials is mentioned, neither an extruded net nor the use of another material to produce bidirectional elasticity is disclosed or suggested.
U.S. Pat. No. 3,791,784 to Arechavaleta discloses an extrusion die fed by two separate polymer streams. Although Arechavaleta suggests that two different materials may be extruded, it is not suggested that the die be used to produce a resulting netting structure which will possess good strand to strand bond, uniform transverse direction strand spacing, or a high transverse direction packing density, i.e., transverse direction strandcount, nor is a net having bidirectional elasticity suggested.
Fabrics, meshes, chain nets, and support materials with elastic properties are disclosed in U.S. Pat. No. 4,107,371 issued to Dean, U.S. Pat. No. 4,673,015 issued to Andreasson, U.S. Pat. No. 4,728,565 issued to Fontana, U.S. Pat. No. 4,469,739 issued to Gretzinger, and U.S. Pat. No. 4,351,872 issued to Brosseau et al. These products are expensive to produce, and are significantly different from a fiber formed extruded netting product.
U.S. Pat. No. 4,107,371 issued to Dean on Aug. 15, 1978 discloses a fabric woven of plastic-coated yarn and polymer strands that is relatively stiff in one direction and relatively flexible in the other direction. This differs from the present invention in that it does not disclose, teach or suggest making an extruded net from two different polymer compositions as between crossing strands.
U.S. Pat. No. 4,351,872 issued to Brosseau et al. on Sep. 28, 1982 discloses a unidirectional stretch mesh laminate used in an orthopaedic traction harness. A commercially available DuPont unidirectional stretch mesh is discussed at col. 3, lines 12-18 as a component of the invention. No patent was found disclosing said mesh.
U.S. Pat. No. 4,469,739 issued to Gretzinger on Sep. 4, 1984 discloses an oriented woven furniture support material made in part from an elastomer monofilament and in part from polymeric material or natural yarn. Unlike the extruded bicomponent elastomeric netting of the present invention, this material is woven rather than a fiber formed extruded product, and is not of a polymeric material.
U.S. Pat. No. 4,673,015 issued to Andreasson on Jun. 16, 1987 discloses a chain net which may include links of elastically deformable material. It is suggested that although warp and weft strands are usually made of links of similarly elastic material, the weft strands may alternatively be made of other material (col. 2, lines 49-64). This patent does not disclose an extruded net.
U.S. Pat. No. 4,728,565 issued to Fontana on Mar. 1, 1988 discloses an elastic support member for supporting stuffing of furniture pieces comprising an elastic net or belt formed of a net or honeycomb fabric or a woven fabric comprised of rubber threads arranged in at least one of the transverse and longitudinal directions. This patent is an improvement of Italian Patent No. 955,134. Although the appearance of rubber threads in at least one direction suggests elasticity, this patent neither discloses nor suggests an extruded net as in the presently disclosed invention.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is "prior art" with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent prior art information exists.